Personal monitor devices encompass devices which are carried on the user's person and are configured to monitor the user or the user's environment in order to determine whether the user is in danger. They are particularly, but not exclusively, used to monitor lone workers.
Lone worker monitoring is the practice of monitoring the safety of employees who may be exposed to risk due to work conditions in which they are located out of sight and sound from a person who may be able to offer aid in the event of an emergency.
In some areas, including certain Provinces in Canada and the United Kingdom, legislation has driven the adoption of lone worker policies as well as methods of monitoring the safety of these employees.
A worker may be considered to be working alone if the worker works by himself or herself at a work site in circumstances where assistance is not readily available when needed. In the past, employers could eliminate the risk of workers working alone, as well as the need to comply with the working alone requirements, if they chose to organize work schedules and workplace procedures to eliminate the need for workers to work by themselves. However, in many job and/or field situations this is not always possible.
Other methods have been developed to mitigate the risks to lone workers. These methods include:                Phone-based check-in systems. Employees are required to call in to a designated receiver after a predetermined time. Check-ins are often performed hourly or bi-hourly.        Buddy systems. Employees may be paired up to perform certain tasks. Theoretically, should an emergency occur and one of the employees be rendered incapacitated, the other would remain available to call for help and provide aid. This system may be less reliable in cases where the threat can incapacitate both workers simultaneously (e.g. oxygen deficient and/or toxic gas environments).        Safety monitoring smartphone applications. With the widespread adoption of smart phones, the deployment of a dedicated application allowing employees to quickly request aid has become more feasible. These applications may provide a panic button or allow for prompt check-in without requiring a phone call to be made. This system may not be optimal where the threat is not detectable before it becomes dangerous (e.g. carbon monoxide gas is odourless and so may not be detected by the worker before they succumb).        Safety monitoring devices. Dedicated monitoring devices have become a new best practice in employee safety monitoring. Typically, products of this type offer multiple methods of alerting including both automated and manual methods.        
Gas detectors come packaged into two main form factors: portable devices and fixed gas detectors. Fixed type gas detectors are generally mounted near the process area of a plant or control room, or an area to be monitored. These industrial sensors are generally installed on fixed structures and connected by way of a supervisory control and data acquisition (SCADA) system for remote monitoring. The SCADA control operates with coded signals over a communication channel system for continuous monitoring (using typically one communication channel per remote station). On the other hand, portable detectors are used to monitor the atmosphere around personnel by affixing the gas detector to their clothing such as mounting on a waist belt. These gas detectors allow the individual to know, by way of transmitted warnings such as audible and visible signals, when dangerous levels of gas vapors are detected.
As noted above, it has long been established that monitoring of gas concentrations in an ambient atmosphere for a particular area or region is essential for the safety of the people working in those areas or regions. A natural or man-made gas leak could result in the toxic exposure of an individual, and thus detecting the leak is essential to the well-being and safety of the individual or individuals in the exposed area.
In order for gas instruments to adequately measure and indicate risk, systems for monitoring on-going processes often correspond to a baseline signature and compare the current atmospheric signature to that established baseline. A deviation from comparison of the baseline to the atmospheric signature can be effective at eliciting a response to a potentially lethal exposure; or, alerting the individual to other atmospheric risk based on the sensor measurements.
It will be appreciated that monitor systems may be used in situations where people are not working alone (e.g. working in teams; refinery workers, water treatment plants etc.)